Inactivation in Kv channels plays a key role in dynamic regulation of neuronal excitability. Multifunctional auxiliary subunit KChIPs1-4 co-assemble with pore-forming rapidly inactivating Kv4 α subunits to form a native complex that encodes somatodentritic A-type K+ current in neurons. KChIP1 increases Kv4 surface expression, speeds up steady-state inactivation with a moderate effect on fast inactivation. In contrast, KChIP4 variant KChIP4a functions as a suppressor of inactivation to eliminate the fast inactivation of Kv4 channels, but neither promotes surface expression nor has any effect on recovery time constant. We have recently determined the crystal structure of KChIP4a that reveals a distinct hydrophobic N-terminus as well as a core structure showing overlap with known KChIP1. In this study, we transfected HEK 293 cells that were solubilized andFast Protein Liquid Chromatography (FPLC) analysis was performed with Size Exclusion Chromatography (SEC) using a Superdex 200 column. The SEC-FPLC assay reveals that KChIP4a proteins self-associate to form multimers with three peaks, compared with a single peak of KChIP1 dominated by monomer. Mutations in N-terminal key residues of KChIP4a can turn multimeric proteins into monomers with a single peak on SEC. Two-electrode voltage clamp in oocytes confirms that disruption of multimeric state of KChIP4a proteins can convert its non-inactivating function into fast inactivating like KChIP1. Taken together, our findings of key residues in N-terminal KChIP4a critical for conversion between fast and slow inactivation may be a site of action for chemical compounds that can alter channel inactivation for a potential therapy of membrane excitability-related disorders.